This invention relates to NMR imaging methods and has particular application in methods of obtaining NMR imaging information from solid objects.
The NMR imaging of solid and other materials which have short spin-spin relaxation times has not been developed to the same level of sophistication as the NMR imaging of liquid and quasi-liquid materials. This is because of the inherently greater linewidth in solids compared to liquids which forces the use of excessively large magnetic field gradients in prohibitively short times if traditional techniques are to be adopted. One kind of method that has been proposed to overcome the difficulties associated with imaging in solids uses multipulse sequences to provide line narrowing. However, the biggest drawback with multipulse sequencing concerns the large radio-frequency pulse power which is required. In part at least this is needed to overcome the large spectral width in an imaging experiment resulting from the presence of magnetic field gradients during the time of application of rf pulses.